We will measure the concentrations, compositions, and metabolism of different lipoproteins in relation to the development of atherosclerosis in squirrel, cebus monkeys and rabbits and of gallstones in squirrel monkeys. We will in particular emphasize the role of diet and the importance of sex and the sex hormones. Ultracentrifugation is the primary means for separation of lipoproteins. In addition to analysis of the different subfractions, we will label the apoprotein moieties with 125I and reinject them into recipients from different diet or sex categories which vary in the degree of elevation of blood lipids and severity of atherosclerosis. We are also investigating the fate of 125I-lipoproteins in isolated systems, particularly isolated livers and isolated hepatocytes. Since squirrel monkeys also develop gallstones we will correlate lipoprotein patterns and gallstone incidence and biliary physiology.